Recovery of sulfur compounds from petroleum



Feb. 5, 1-952 R. E. BARIEAU RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUMFiled July 15, 1948 2 SHEETS-SHEET l m 3.": 3m .0 FIUUZ w 5 w 0 L .n m mm GII'P E E W N D H M Y. a R A w w w a S c I T H m, f E w v 0 m w 0 E wl 2O MOLES HF PER GRAM ATOM OF SULFUR CHARGED INVENTOR ROBERT E. BARIEAUFIG. 1

ATTORNYS/ Feb. 1952 R. E. BARIEAU 2, 8

RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUM Filed July 15, 1948 2SHEETSSHEET 2 .97 .96 'l .95 l0 0 N 94F T 0/4 I 5.93 5 l :5 Q. a Li. 5'.9! w

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l .9 \N l-r o v :1 I00 0 l0 3 u m z I-- 2 Q HF STRENGTH WEIGHT 7INVENTOR ROBERT E. PSARIEAU 2 mam r ATTORNEY Patented Feb. 5, 1952UNITED RECOVERY OF SULFUR COMPOUNDS FROM PETROLEUM Application July 13,1948, Serial No. 38,397

8 Claims.

This invention relates to a method of extractmg sulfur compounds fromcrude petroleum oils or from distillation fractions of these crude oils.More particularly, this invention relates to a method of separatingsulfur compounds from petroleum crude oils or fractions thereof having amedium to high sulfur content by a two-stage acid extraction process.

An object of this invention is to recover a concentrate consistingpredominantly of organic sulfur compounds from crude petroleum oils orfractions of crude petroleum oils.

A further object is to effect a substantial degree of desulfurization ofcrude petroleum or fractions of crude petroleum by concentrating thesulfur compounds contained therein in an extract by means of a two-stageacid extraction process.

A variety of sulfur compounds have been identified in petroleum oils andcrude concentrates of these compounds are known to be useful in thepreparation of weed-killing compositions and surface-active agents. Suchconcentrates may be further processed to separate sulfur compoundsindividually or according to chemical type.

It has been discovered that an extract consisting predominantly oforganic sulfur compounds can be obtained from crude petroleum oils orpetroleum fractions by a method comprising a two-stage acid extractionwherein the concentration of the acid used in the first extraction stepis lower than that of the acid used in the second extraction step.

It has also been discovered that the acid of lower concentration used inthe first extraction step removes from petroleum stocks of medium tohigh sulfur content, components of these stocks which are of anon-sulfurous nature. The extract containing the non-sulfurouscomponents is, small in volume and has a relatively low overallsulfurcontent. Thus, the acid of lower concentration effects a selectiveremoval of the nonsulfurous components, which would be. removed togetherwith and as an impurity in such sulfur compounds that might be extractedin a single extraction employing a more concentrated acid.

Extraction of the rafiinate of the first extraction step with an acid ofhigher concentration has been found to produce an extract containing ahigher percentage of sulfur compounds than it is possible to obtain in asingle extraction.

Further, it has been discovered that there exist preferred acids andacid concentration ranges for both extraction steps.

The mineral acids are particularly suitable for use in the firstextraction step; especially strong mineral acids such as hydrofluoric,perchloric, and sulfuric acids. From data gathered in the extraction ofSanta Maria gas oils with these acids, concentrations of between aboutto about per cent in the first extraction step can be used with thepreferred concentrations being:

Per cent Hydrofluoric acid 80 Sulfuric acid 80 Perchloric acid 70Hydofluoric acid is employed in the second extraction step at aconcentration of at least per cent and preferably at a concentration ofabout 8586%.

The first extraction step in the process of the invention produces anextract consisting principally of readily extractable non-sulfurcompounds, while the second step produces an extract consistingpredominantly of sulfur compounds.

The three acids which may be employed in the first extraction step areapproximately equivalent in their extractive action; however, thepreferred concentrations .difier for the acids as shown above.

Generally it is preferredto conduct both extraction steps under normalconditions of temperature and under sufficient pressure to maintain thematerials in liquid phase. However, it is possible to conduct theextractions at reduced or elevated temperaturesprovided the pressure Thecontact time in both extraction steps is ordinarily short, being on theorder of ten minutes; however, some stocks may require a longer periodof contact for successful extraction.

The ratio of acid to oil in the first extraction is preferably betweenabout 0.05 and 0.3 volume of acid per volume of oil.

The ratio of hydrofluoric acid to oil in the second extraction step mayvary from about 2 to 20 mols of acid per gram-atom of extractable sulfurcontained in the rafi'inate of the first extraction step but it ispreferred to use a ratio of 14-16 moles of HF per gram-atom ofextractable sulfur contained in the raffinate of the first extractionstep.

Both extraction steps may be conducted in either batchwise or continuousoperation, and the conventional apparatus of the solvent extraction artmay be readily adapted for use in the process of the invention. One ofthe methods of conducting this two-step extraction process, when usinghydrofluoric acid in both steps, is to use the acid phase from thesecond extraction step, after it has been suitably purified and diluted,as the solvent-extractive phase for the first extraction step; thenpurifying and concentrating the acid from this latter step to asuificient strength and purity so that it can be recycled and used asthe acid for the second ste thereby eliminating the necessity of twoacid concentration units. Such util zation of hydrofluoric acid in bothextraction steps permits more efiioient use of the acid solvent and simlifies solvent recovery and purification. Accord n ly,

the modification of the process of the inv ntion is preferred over moifications employing different acids in the two extraction steps.

The second extract from either cont nu us or batch-type operation may befurther treated to separate the sulfur com ounds individually or acc rdng to chemical type.

Of the appended drawin s, Fi ure 1 is a g aphical re resentation of thevariations of the cha acter of the extract obtained from a highsulfurgas oil with quantity of acid employed in the extraction step. Figure 2is a graph cal rep esentation of the variation in the pro erties of theextract with the concentration of the acid employed.

Referring now to Figure 1. the data upon which the graph is based wasgathered in a series of experiments to which a Santa Maria gas oil havina sulfur content of 2.46 per cent was extracted with varying Quantitiesof 99.4 per cent hydrofluoric acid. The acid quantity is expressed inmols of acid per gram-atom of sulfur in the oil being extracted. It isseen that the extract yield rises sharply as the quantity of ac demployed is increased, this sharp rise continues until a ratio of 14-16mols of acid per gram-atom of sulfur is reached. The employment ofhigher acid to sulfur ratios produces only a slight increase in theyield of extract. The weight per cent of sulfur in the extract similarlyshows a sharp rise as the ratio of acid to sulfur is increased from to 8mols of acid per gram-atom of extractable sulfur. The rise continuesless sharply until a ratio of about 1 1 mols of acid per gram-atom ofsulfur is reached after which further increases in the acid ratioproduce little gain in the sulfur content of the extract. It is foundthat most efficient use of the acid in the extraction of sulfurcompounds is obtained by employing 14-16 mols of acid per gram-atom ofextractable sulfur in the extraction.

In Figure 2 of the appended drawings, data accumulated in a series ofextractions of Santa Maria gas oil containing 2.46 per cent sulfur issummarized. A ratio of 14.8 mols of acid to each gram-atom of sulfur inthe oil was maintained in each extraction and the concentration ofhydrofluoric acid was varied from to 99.4 per cent by weight. It is seenfrom this figure that the extract yield increased slowly with acid concentration until a concentration of -80 per cent was reached and thenthe yield increased much more rapidly with further increases inconcentration. The per cent of sulfur in the extracted material alsoincreased slowly with acid concen tration until a concentration of aboutper cent was reached and then rose abruptly to reach a maximum at about86 per cent. As acid concentration was increased above 86 per cent andparticularly as it was increased above 90 per cent, the percentage ofsulfur in the extract declined. The extract obtainedat acidconcentrations from 50 to 80 per cent is small in volume and low insulfur content indicating the presence in the oil of some non-sulfurousmaterial, which is rather easily extractable. The decline in per centsulfur content of the extract obtained at acid concentrations aboveabout 90 per cent indicates the probability that some difficultlyextractable non sulfurous materials are removed by hydrofluoric acid at90-100 per cent concentrations. Operation according to the process ofthe invention in its preferred modification employing hydrofluoric acidat about 80 per cent concentration in a first extraction step makespossible the removal of readily extractable non-sulfurous compounds in.this step, then a second extraction step employing hydrofluoric acid ata concentration of -90 per cent makes possible the removal of an extractconsisting essentially of sulfur compounds without the inclusion of thedifficultly extractable non-sulfurous material which would be removed ifacid at concentrations above per cent were employed. While acidconcentrations of 85-90 per cent are preferred in the second extractionstep, the process may be conducted employing more concentrated or evensubstantially anhydrous hydrofluoric acid in the second extraction stepin order to obtain the advantage of greater concurrent desulfurizationof the oil in addition to the recovery of an extract consistingpredominantly of sulfur compounds.

The process of the invention is illustrated by the following examples:

EXAMPLE I Santa Maria oil was extracted according to the process of theinvention employing perchloric; acid of 70-72 per cent concentration inthe first extraction step and hydrofluoric acid of 85.7 per centconcentration in the second extraction step. Properties of this gas oilare shown in the following Table I. The gas oil and perchloric acid wereshaken in a laboratory separatory funnel for 5-10 minutes. Afterstanding, the extract layer was separated. The rafiinate was washed withwater, then with caustic, and then with water again. After washing, therafdnate was filtered. andinspected. Following inspection, the raffinatewas extracted with 85.7 per cent hydrofluoric acid in a manner similarto that of the first extraction step. The raflinate and extract of thesecond extraction were washed and inspected. Data from this experimentare sum-- manned in the following Table I. Y

more I Extraction 1 Extraction 2 Substance treated Santa Maria gas oilRai'linate of Extractions. A d Perchlorlc. Hydrogen Fluoride. AcidStrength (Wt per cent) 70-72 85.7. Pretreatment Caustic Wash" Contacttime. 5-10 minutes minutes. Temperature 7 79-84. Moles of HF per g. atomof S 15.7. Vol. acid per Vol. Charge 0.100

Inspections Charge Extract Rafiinate Charge Extract Raflinate ActualRecovery (Wt. per cent). Yield Density (Wt. per cent) Yield from Wt.(Phase separation) Density (/4) 0.8811 Refractive Index (N a). 1. 4887Aniline Point F.)... r 127 Molecula'rWt.-' Carbon (Wt. per cent). 84. 63Hydrogen (Wt. per cent) 12.50 Suhur (Wt. per cent) 2. i6 Nitrogen 0. O5C+H+S (Av. per cent).. C+H+S+N (Av. per ent)..... 99.64 Per Cent SulfurCompounds..

Note: 1 Yield from Density (Wt. per cent) is calculated in the followingmanner:

where:

D.,: density of charge. Dr=density of rafliuate. D. density of extract.

2 ll'lolecular weights were determined from observations of the freezingpoint lowering of benzene in benzene solutions of the materials whosemolecular weight is being determined.

The method is set forth in Physical Methods of Organic Chemistry, byWeissbcrgcr, Inter-s ien e Press, 1945, at page et seq.

It is seen from Table I that an extract containing 81.3 per cent sulfurcompounds was ob- :15

tained in the sccondextraction step and that a substantial degree ofdesulfurization of the gas oil was concurrently obtained.

EXAMPLE II A quantity of Santa Maria gas oil was subjected to atwo-stage acid extraction employing hydrofluoric acid as the extractivesolvent in both stages, the acid concentration was 80.4 per cent in thefirst stage and 85.9 per cent in the second stage. The results of theextractions are pcrchloric acid of '70 per cent concentration areapproximately equivalent in the first extraction step of the process ofthis invention and it has similarly been found that sulfuric acid ofabout 88 per cent concentration is approximately equivalent tohydrofluoric and perchloric acids at their respective preferredconcentrations in the first extraction step.

It is not intended that this invention be limited to the examples givenfor the sake of illustration but rather to extend it to suchmodifications Within the skill of the art as are within the scope of theappended claims.

summarized in the following Table II: I claim:

Table II Extraction 2 Extraction 1 Raflinate of Extraction 1 Substancetreated Santa Maria gas oil Santa Maria gas oil, pretreated with 80.4%HF. HF Strength (Wt. Per Cent) 4 85.9. Pretreatment Contact timeTemperature E)... Moles of HF per g. atom of S Inspection Charge ExtractRailinate Charge Extract Raflinate Actual Rccovery (wt. per cent)..-" 4.16 81. 7 100 5. 33 80. 4 Yield from Density (wt. per cent) 100 7. 3 92.7 100 9. 37 90.63 Yield from HF balan e (wt. per

cent) 6. 7 93. 3 100 Yield from Wt. 5.0 95. 0

Density (20/4) 9336 .8772

Refractive Index (N 5135 .4869

Aniline Point F.) Molecular Weight Carbon (Wt. Per Cent C+H+S (Av. PerCent). Per Cent Sulphur Compounds" See Remarks following Table I.

It is seen from Examples I and II that hydrofluoric acid of 80 per centconcentration and 1 The method of separating a. concentrate of 7 organicsulfur compounds from sulfur-containing petroleum oils which comprisesfirst extracting said oil with a mineral acid having a concentration notexceeding 80 per cent by weight and thereafter extracting the raifinateof the first extraction with hydrofluoric acid having a concen' trationof at least 85 per cent by weight.

2. The method of separating a concentrate of organic sulfur compoundsfrom petroleum oils of medium to high sulfur content which comprisesfirst extracting the oil with a strong mineral acid at a concentrationnot exceeding about 80 per cent by weight to remove readily extractablenon-sulfur compounds from the oil and thereafter extracting therafiinate of the first extraction step with hydrofluoric acid at aconcentration of at least per cent by weight to separate an extractconsistingpredominantly of organic sulfur compounds.

3. The method of separating a concentrate of organic sulfur compoundsfrom petroleum oils of medium to high sulfur content which comprisesfirst extracting one volume of oil with 0.05 to 0.3 volumes of a strongmineral acid at a concentration of per cent to per cent by weight toremove readily extractable non-sulfur compounds from the oil andthereafter extracting the rafi'lnate of the first extraction withhydrofluoric acid at a concentration of at least per cent by weight toseparate an extract consisting predominantly of organic sulfurcompounds.

4. The method of separating a concentrate of organic sulfur compoundsfrom petroleum oils of medium to high sulfur content which comprisesfirst extracting one volume of oil with 0.05 to 0.3 volumes of a strongmineral acid at a concentration of about 50 to 80 per cent by weight toremove readily extractable non-sulfur compounds from the oil, thereafterextracting the raffinate of the first extraction with hydrofluoric acidat a concentration of at least 85 per cent by weight to separate anextract consisting predominantly of organic sulfur compounds and employing in the second extraction step 14-16 mols of hydrofluoric acidper gram-atom of extractable sulfur contained in the rafiinate of thefirst extraction step.

5. The method of separating a concentrate of organic sulfur compoundsfrom petroleum oils of medium to high sulfur content which comprisesfirst extracting one volume of oil with 0.05 to 0.3 volumes ofhydrofluoric acid having a concentration of about 80 per cent to removereadily extractable non-sulfur compounds from the oil, thereafterextracting the raifinate of the first extraction step with hydrofluoricacid having a concentration of about'85-90 per cent and employing in thesecond extraction 14-16 mols of hydrofluoric acid per gram-atom ofextractable sulfur contained in the raifinate of the first extractionstep.

6. The method as defined in claim 5 wherein the acid employed in thefirst extraction step is perchloric acid at a concentration of about percent.

7. The method as defined in claim 5 wherein the acid employed in thefirst extraction step is sulfuric acid at a concentration of about percent.

8. The method as defined in claim 5 wherein the petroleumoil is a SantaMaria gas oil.

ROBERT E. BARIEAU.

REFERENCES CITED The following references are'of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,957,840 Lewis May 8, 19342,440,258 Elliott et al Apr. 27, 1948 2,449,463 Evering et a1 Sept. 14,1948 2,465,964 Brooke et a1 Mar. 29, 1949 FOREIGN PATENTS Number CountryDate 345,596 Great Britain Mar. 26, 1931

1. THE METHOD OF SEPARATING A CONCENTRATE OF ORGANIC SULFUR COMPOUNDSFROM SULFUR-CONTAINING PETROLEUM OILS WHICH COMPRISES FIRST EXTRACTINGSAID OIL WITH A MINERAL ACID HAVING A CONCENTRATION NOT EXCEEDING 80 PERCENT BY WEIGHT AND THEREAFTER EXTRACTING THE RAFFINATE OF THE FIRST EX-